A great deal of dust is usually produced in the twisting of filaments in double-thread twisters, in particular when mixtures of natural and synthetic fibers are being used. This is caused by the friction of the thread balloon against a balloon-limiting cylinder surrounding the spindle. The dust is formed by many broken fiber ends which find their way into the machine and thereby degrade the quality of the yarn being produced. In addition, a portion of this dust is conducted by the so-called balloon wind into the area around the machine so as to contaminate the atmosphere. Twisting of filaments with a high coefficient of friction and the use of a balloon-limiting cylinder also increases the stresses on the filament so as further to increase the production of dust. This increased longitudinal stressing of the filament gives a high-quality product but also greatly increases the chance of filament breakage and, therefore, down-time of the machine.
It has been suggested (see German printed specification No. 1,510,521) to provide on the outside of each balloon-limiting cylinder of each spindle a reservoir for a wetting agent that is applied to the balloon through an opening between the reservoir and the interior of the cylinder. A sponge, a wick, a piece of sintered material or the like is used to conduct the wetting agent from the reservoir to the balloon limiter. All the reservoirs are connected to a supply conduit which continuously or periodically refills them. The wetting agent is therefore applied to the thread in the balloon and smooths it so as to lower the coefficient of friction between the thread and the balloon and, therefore, to decrease the production of dust in this region.
In another known system (see German patent No. 1,259,751) it has been suggested to mount on the top of the spindle a cylindrical upwardly open vessel which is filled with a treatment liquid and which is covered with a porous stopper. Several wicks extend downwardly from the stopper into the bottom of the vessel so as to transport the wetting agent upwardly by capillary action. As the thread is pulled from the spool, it passes over the wetted stopper and picks up some of the treatment liquid.
In the prior systems of which we are aware, the wetting of the thread occurs either at a point (e.g. in the balloon) where a certain amount of dust has already been generated or in a manner which is difficult to control and which therefore leads to irregular moistening and the possible spilling of excess liquid onto adjoining parts of the machinery.